Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$55.57	7.386%	$59.6744	$59.67	$59.65	$59.70
Purchase #2	$159.50	7.407%	$171.3142	$171.31	$171.30	$171.30
Purchase #3	$248.63	10.205%	$274.0027	$274.00	$274.00	$274.00
Purchase #4	$12.48	9.218%	$13.6304	$13.63	$13.65	$13.60
Purchase #5	$168.93	10.627%	$186.8822	$186.88	$186.90	$186.90
Purchase #6	$105.77	3.658%	$109.6391	$109.64	$109.65	$109.60
Purchase #7	$59.35	8.181%	$64.2054	$64.21	$64.20	$64.20
7 purchase totals =	$810.23		$879.3484	$879.34	$879.35	$879.30